The present invention relates broadly to a power supply apparatus, and in particular to an autonomous uninterruptable power supply apparatus.
The purpose of an uninterruptable power supply (UPS) is to protect critical electrical loads from transient or steady state outages or disturbances in the primary power source. The basic configuration of a typical, commercially available, uninterruptable power supply is comprised at a minimum of a standby battery and a battery charger and may also include an inverter for AC applications. Systems of this type can be found in most computer installations and laboratory systems which cannot tolerate even momentary disturbances of input power.
Although uninterruptable power supplies currently in use are generally capable of meeting the basic requirement of providing a backup power source there are several problems inherent in their design which make their use in applications requiring high reliability, long life or low maintenance a problem. Existing systems cannot provide a positive indication of battery capability; battery failure is not discovered until after a primary power loss. A unit failure in an existing system can propagate to other parts of the supply; i.e. a charger failure can cause a battery failure. Many existing uninterruptable power supplies require periodic battery maintenance because the battery systems used are not designed for sealed operation. Non-optimum battery charge and float control results in shortened battery life. Accurate status of the uninterruptable power supply can only be determined by periodic, manual system testing.